Leek

Leeks need loose, well-drained, fertile soil in full sun and grow best around 18-21°C (65-70°F). Seed is sown shallowly, either direct or in a dense seed-bed for later transplanting once seedlings reach pencil thickness, with plants spaced a few inches apart in rows a foot or more apart. Regular weekly watering to a good depth keeps growth even, and a nitrogen side-dressing during the season supports leaf and stem development.

To lengthen the edible white shank, soil or mulch is gradually mounded up around the stem as it grows, a technique known as blanching; this begins only once stems have reached about pencil thickness. Beds should be kept weed-free by careful shallow cultivation so the roots are not disturbed. Leeks tolerate standing in the field for an extended period and can be left in place for up to six months from planting before harvest.

Leeks are attacked by onion maggots, thrips and the leek moth, with thrips damage worst when plants are drought-stressed in hot weather; slugs can damage young seedlings. Fungal diseases include leek rust, botrytis leaf blight, downy mildew, purple blotch and pink root, along with damping-off of seedlings and general leaf spot; overly wet or poorly drained soil can cause rot. Management relies on wide spacing for airflow, crop rotation away from other alliums for several years, disease-free seed, and removal of infected debris.

Leeks develop slowly, generally taking around 100 to 120 days to mature, and are ready when the stem has thickened to about an inch in diameter. They are lifted by loosening the soil with a fork and pulling the plant free rather than cutting the top growth.

Leeks are grown as a cooked vegetable, their thick leaf bases and mildly onion-flavoured stem used in soups and many other dishes as a milder substitute for onion.

In Wales, the leek carries a traditional and symbolic association dating to a 7th-century battle in which Welsh soldiers reportedly wore pieces of leek to distinguish themselves from Saxon opponents, a link still marked by the wearing of a leek on St. David's Day.

The leek was developed from a wild type native to Western Asia and the Mediterranean, with wild forms already used as food in the early Bronze Age around 4000 BC and likely domesticated by about 2000 BC. It was part of the diet of workers who built the Egyptian pyramids and has been cultivated in Western Europe since the Middle Ages, later being carried to North America by European settlers.